In motion-picture and television cameras, the horizontal and-azimuthal panning shooting movements are separately controlled, and a double braking system is therefore necessary.
In fact, within the scope of technologies already known from prior art, fluid operated heads are known which, for their braking force, use the braking effect of a high viscosity fluid.
These include two kinds of devices, the first of which utilizes the force that is produced between two surfaces, in particular coaxial cylinders, which rotate with respect to each other.
Such a solution, though excluding any possibility of friction, does not allow adjustment of the magnitude of the braking force.
The second kind of device utilizes as its braking system the principle of two surfaces which move with respect to each other with an interposed high viscosity fluid, but also exploits the compression of the fluid and the friction between the rotor and the stator to vary resistance.
Moreover, jaw systems are known of the kind used for the brakes of motorcycles, operating in a tight seal box in a viscous fluid bath.
In such devices, by increasing the pressure of the jaws on the drum, an increase of the resistance to motion is achieved. The main drawback of such a system is that, since the fluid effect and the friction effect are combined, the system undergoes considerable variations as regards its efficiency according to temperature, wear and force applied by the arm of the operator.
A further solution adopted by other manufacturers to obtain such a braking effect makes use of a steel tape on a drum. By pulling the tape by a side, one obtains a variable pressure on the drum and therefore a variation of resistance.
In both systems, the surfaces of the jaws and of the tape are coated with a cork layer, the wrinkled surface whereof delays the lateral expulsion of the fluid subject to pressure.
The main disadvantages of such devices reside in the fact that when the cameraman repeats a panning motion several times in rapid succession, the pressure produced on the fluid veil by the jaws or by the tape produces an expulsion of the fluid, causing the braking effect to decrease during the operation, and thereby compromising in an absolute manner the quality of the shots and rendering duplication practically impossible.
Finally, there are support heads in which the braking force is provided by series arranged modular members in a high viscosity grease bath. The braking effect in various gradations is obtained as a consequence of the engagement or disengagement of the modules. Such a system, acting in absolute absence of friction, ensures continuity, the absence of vibrations and the graduality of motion required in professional shootings, but does not allow the magnitude of the braking force to be changed simultaneously with the panning shot itself, since the engagement of a different number of modules would produce a jump in the shooting.
It turns out to be essential to have a support head of motion picture or television cameras that overcomes the drawbacks of the aforementioned technologies and allows control of horizontal and azimuthal panning shot movements, in absolute absence of friction, adjustable from a minimum to a maximum and repeatable according to the requirements of the operator, as well as simultaneous control of the balancing of the head itself, in absolute absence of vibrations, with graduality and also without any friction during operation.